Grape Sugar. (Glucose, Dextrose.)
Soxhlet, J.prakt. C/i., 1880, (2) 21, 245.
250 grms. cane sugar.
750 c.c. spirit.
30 c.c. cone, hydrochloric acid.
The spirit and acid are mixed and warmed to 45—50°, whilst
the iincly*po\vclercd cane-sugar is gradually added and stirred.
When the sugar has dissolved the solution is cooled, and a few
crystals of anhydrous grape-sugar added. On standing for a
day or two the grape-sugar deposits in the form of fine crystals,
which continue to increase in quantity. When no further de-
position is observed, the crystals arc filtered and washed with
spirit. The sugar may be purified by dissolving in a little
water to a syrup, and adding hot methyl alcohol until a turbidity
appears. On cooling, the grape-sugar crystallises out.
Cum; sugar. (llucosc. I'Yuctuse.
Properties.—Colourless crystals ; m. p. 146° ; soluble in hot
and cold water, insoluble in alcohol.
AVmvVVw.v.•—i. Add to a little of the solution of glucose a few
drops of caustic soda, and warm. The colour changes from
yellow to brown.
2. Add to 2 or 3 c.c. of the solution two or three drops of copper
sulphate, and then caustic soda, until a clear blue solution is
obtained, and heat to boiling. Red cuprous oxide is precipi-
3. Add a few drops of glucose solution to half a test-tube
of ammonio-silvcr nitrate solution and place the test-tube in
hot water. A mirror of metallic silver is formed.
4. Dissolve about 0*5 grain of glucose in 5 c.c. of water, and
add a solution of phenylhydrazine acetate, made by dissolving
i gram of phenylhydnizine in the same weight ofjjlacial acetic
acid, and diluting to 5 e,c, Mix live solatia^ and warm in the,